First we need to convert the dimensions of the room to a volume: V = 3m x 4m x 5m = 60 cubic meters
We also need to convert the temperature in degrees celsius to kelvins by adding 273.15: T = 293.15K
We use the ideal gas law to find the number of moles 'n' there are in the room at the given temperature and pressure:
We know the mass per mole ratio, so we just multiply:
